The instant invention relates to a process to guide, hold, and cut a yarn during bobbin replacement in a spinning and winding machine in which a continuously fed yarn is wound into a cross-wound bobbin and is conveyed into a lateral area next to the winding zone when a predetermined diameter of the cross-wound bobbin has been reached, until after completion of the replacement of the full cross-wound bobbin by an empty bobbin holder.
It is known that in order to convey the yarn continuously fed by from a spinning station to a winding station, additional mechanical and pneumatic yarn guides are used which remove the yarn from the yarn guide assigned to the winding process and convey it into a lateral area until bobbin replacement is completed (See German Patent Publication No. DE-OS 2,445,182).
These additional yarn guides are pivoted via actuation rods and rams from their rest position into their work position and hold the yarn away from the winding station. The yarn, which continues to be fed during that time, is taken up by a suction device. When the full cross-wound bobbin has been replaced by an empty bobbin former, the yarn is conveyed to a yarn clamping device, the yarn end is cut off with scissors and the rotation of the bobbin former is then started up.
The disadvantage with this device is the great number of mechanical means which must be driven in order to obtain the movements required for the conveying of the yarn. The great number of actuating rods and rams require extensive assembly and maintenance work resulting in production losses and high costs. This is especially true with spinning machines operating at high spinning speeds in which bobbin replacement and stoppage of the winding device must be kept as low as possible, since the yarn spun during bobbin replacement cannot be used for winding. Stopping the spinning process and subsequent re-piecing would be too expensive with open-end spinning machines.
The utilization of additional yarn guides which must seize the yarn for bobbin replacement results in a further disadvantage. Especially where high spinning and winding speeds, such as are obtained with open-end spinning machines are involved, the cross-winding speed is such that yarn transfer from the cross-winding guide to the additional yarn guide is not ensured. When the transfer of the yarn fails, valuable production time is lost and cross-wound bobbins which are too full or are not properly wound are produced.
A further disadvantage for the formation of the bobbin consists in the fact that the bobbin holder is accelerated by the release of a shoe brake after the yarn has been clamped. This results in poor yarn winding at constant yarn feeding speed because the yarn tension between bobbin former and winding station is uneven during the beginning of the winding process.
The process described in German Patent Publication No. DE-OS 3,411,158 uses an auxiliary yarn guide to convey the yarn during bobbin replacement, but this auxiliary yarn guide must be pivoted into a working position just as the additional yarn guide described earlier. The required movement sequence consists of several rotational and longitudinal movements and results in increased control, assembly and maintenance requirements. Following bobbin replacement, the yarn is placed into a yarn-catching notch on the empty holder where it is clamped. The yarn spun at the spinning station during bobbin placement is then torn off. This has the disadvantage that it is not possible to determine precisely at which point the yarn is torn, and it is thus possible that the yarn will break at the clamping point on the bobbin holder, or that it will be pulled back out of the clamping point. When this occurs, the yarn must be seized again and the clamping process must be repeated, leading to considerable time loss and lost productivity of the winding machine.
German Patent Publication No. DE-OS 2,230,947 shows a device in which a step motor takes over the cross-winding movement of a yarn guide. The cross-winding speed changes as a function of the rotational speed of the cross-wind bobbin. The signals for speed changes are detected by electromagnetic and electronic means. The yarn guide is driven via a shaft and moves back and forth in front of the winding zone. The disadvantage of this device is the great expenditure for signal detection as well as for the reversal of a first translational movement into a second translational movement which is contrary to the first one. This device is also suitable only for cross-winding, and not for assisting in the bobbin replacement, since a rotational movement of the cross-wound bobbin or of the element which drives the cross-wound bobbin is always a condition for the control of the step motor.